1. Field of the Invention
The present invention relates to a transmission used for automobiles, agricultural machinery, construction machinery, and industrial machinery, among some others. More particularly, the invention relates to the ratchet one-way clutch that uses ratchet (pawl member) for a lock mechanism, among the one-way clutches used for an automatic transmission or the like adopted for vehicles to carry out the function of back stop or the like. More specifically, the invention relates to a ratchet one-way clutch provided with means for reducing the drag torque of bearing.
2. Related Background Art
In general, the one-way clutch used for the automatic transmission is provided with the outer race and inner race that rotate relatively, and arranged to transmit the rotational torque only in one direction by allowing the sprag, roller, and others, which transmit the torque between the outer and inner races, to engage with the surface of a cam provided for the raceway surface of the outer race or the inner race. Also, the structure is arranged so that the clutch makes idle rotation in the reverse direction.
Of the one-way clutches thus arranged, there is the ratchet one-way clutch that uses the ratchet as a torque transmission member that transmits torque between the outer and inner races. The ratchet one-way clutch comprises the outer race with pockets on the inner circumference thereof; the inner race with notches on the outer circumference thereof arranged coaxially with the outer race; the pawl member that transmits torque between the inner and outer races in a state of being engaged with each notch of the inner race housed in the pocket so as to lock the one-way clutch; and the elastic member such as a spring that biases the pawl member to the inner race.
The pawl member of the ratchet one-way clutch thus structured is made slidable freely on the outer circumference of the inner race when the one-way clutch rotates in one direction, thus enabling the outer race and inner race to relatively rotate idly. Then, when the one-way clutch begins to rotate in the other direction, the pawl member engages with the notch so that the one-way clutch is conditioned to be locked up.
It has been proposed to incorporate the ratchet one-way clutch in the stator of a torque converter.
For example, in the specification of U.S. Pat. No. 5,947,245, it has been proposed that the clutch of this type is used for the stator of a torque converter of an automobile automatic transmission. FIG. 8 is a sectional view which shows the conventional one-way clutch, taken in the axial direction. Also, FIG. 9 is a front view of the one-way clutch shown in FIG. 8.
As shown in FIG. 8 and FIG. 9, the stator 1 comprises an inner race 3 which engages with a stator shaft (not shown) installed on the inner circumference by use of a spline 9; a runner 8 provided with an outer race portion 4 on the inner circumferential side; pawl members 2, and springs 10 arranged respectively for each of the pockets 21 and 22 (see FIG. 9) installed on the outer race portion 4. Each spring 10 is prevented by a bush 31 from falling off in the axial direction. The bush 31 is fixed by use of a snap spring 5. Also, the end faces of the outer race 4 and the bush 31 in the axial direction are supported by the thrust bearing 7, respectively.
For the conventional one-way clutch thus structured, the bearing, that is, the inner circumferential sliding face of the bush 31, generates the dragging torque due to the influence of oil pressure exerted by the slidable movement thereof on the outer circumferential face 24 of the inner race 3, and the eccentric rotation. Particularly, the contact area is large for the inner circumference of slidably movable face of the bush 31, and the outer circumferential face 24 of the inner race 3. As a result, it is made difficult to reduce the dragging torque.
Also, due to this large contact area, there is a fear to impede the distribution of lubricant that lubricates the acting members centering on the pawl members 2 and notches 23. Further, it has not been sufficient to take measures in making the clutch light in weight and improving the fixing precision, among some others.
Now, therefore, it is an object of the present invention to provide a ratchet one-way clutch for which the dragging torque is made reducible, while the lubricating capability thereof is made attainable. It is another object of the invention to provide a ratchet one-way clutch for which it is attained to make the clutch light in weight, while enhancing the fixing precision thereof.
In order to achieve the objects described above, the ratchet one-way clutch of the present invention comprises an inner race and an outer race coaxially arranged to be relatively rotative; a pawl member arranged between the inner race and outer race to be fitted into a recessed portion provided for the outer circumferential face of the inner race or the inner circumferential face of the outer race for transmitting torque; a spring for biasing the pawl member to the recessed portion; and a bush for supporting the pawl member and spring axially and for providing a bearing between the inner race and outer race. For this clutch, a recessed portion is formed on the inner circumferential face of the bush.
Also, in accordance with the invention, an extrusion is provided for the outer circumference of the aforesaid bush to protrude outwardly in the diametral direction, and the bush is fixed by the extrusion being fitted into a recess portion provided for the outer race.
Further, in accordance with the invention, the aforesaid bush is provided on both ends in the axial direction of the ratchet one-way clutch.
The ratchet one-way clutch of the invention further comprises a block bearing provided at the inner circumference of the outer race.
In accordance with the invention, the ratchet one-way clutch comprises an inner race and an outer race coaxially arranged to be relatively rotative; a pawl member arranged between the inner race and outer race to be fitted into a recessed portion provided for the outer circumferential face of the inner race or the inner circumferential face of the outer race for transmitting torque; a spring for biasing the pawl member to the recessed portion; and a block bearing provided at the inner circumference of the outer race.
Also, in accordance with the invention, the aforesaid block bearing is provided with a through hole penetrating in the axial direction.
Also, in accordance with the invention, a second through hole is provided to penetrate from the aforesaid through hole to the inner race side.
Also, in accordance with the invention, the aforesaid block bearing is provided with an extrusion on the side portion thereof to protrude outwardly in the circumferential direction, and the block bearing is fixed by the extrusion being fitted into a recess portion arranged for the outer race.
The ratchet one-way clutch of the invention further comprises a bush for supporting the pawl member and spring in the axial direction and for providing a bearing between the inner race and outer race. For this clutch, a recessed portion is formed on the inner circumferential face of the bush.
In accordance with the invention, it becomes possible to reduce the contact area between the slidably movable inner circumferential face of the bearing and the outer circumferential face of the inner race, and also, to release the oil pressure which is exerted by minute eccentric rotation. Therefore, the dragging torque that may be generated can be reduced.
Also, with the smaller contact area thus provided, the distribution of lubricant oil is made in good condition to lubricate the operating members centering on the pawl member and recessed portion. Further, it becomes attainable to make the clutch lighter, as well as to enhance the fixing precision.